1. Field of the Invention
The present invention relates to threshold circuits and particularly to multi-channel adaptive threshold circuits wherein the positive responses of all channels are combined and detected by a common threshold detection circuit without combining the noise of the respective channels.
2. Prior Art
In a multi-channel system such as a target detector, infrared, laser, or radar signals are generally detected, applied to individual threshold circuits and then combined in a logic array. While such an approach is generally effective, substantial circuit complexity and expense is involved. In order to alleviate such complexity and expense, simplified threshold circuits have been developed which combine the signals prior to the basic thresholding operation. However, this has been done with simple summing networks which sum the noise as well as the signals thereby causing a significant degeneration in the signal-to-noise ratio.
The present invention is a circuit configured such that the signals can be combined prior to the basic thresholding circuit without any significant loss in the signal-to-noise ratio while significantly decreasing the number of components which have been required by previous approaches. In addition, a simple adaptive threshold circuit is also provided as an integral part of the circuit with no additional parts required.
Although a single channel adapative threshold circuit such as that shown in FIG. 3 is known, in prior systems when a plurality of channels existed, each had its own independent thresholding circuit. However, the present invention makes use of the previously unrecognized fact that the signal-to-noise ratio is largely unaffected if a plurality of channels are coupled in parallel to a single thresholding circuit or that the noise of any single channel has very minimal influence on the thresholding capability of any other channel because each has its own individual adaptive thresholding capacitor which is charged solely from its own input signal.